Implemented gregorian date support, major refactor of bucket
calculations. Further separated redis-only features from mongo
implementation.
Changed the API to Timeseries.series() to support start and end timestamps
Documentation on gregorian intervals
Adding back support for weekly intervals with strptime workaround
Implemented handling of gregorian time configurations
More tests for gregorian dates and new parameters to series()
Fixed mongo series implementation to return missing time intervals
Documentation on new series() API and how to delete data